JP6609755B2 - Nickel ultrafine particle production method and apparatus, and fine particle - Google Patents

Description

  The present invention relates to a method and apparatus for producing nickel ultrafine particles and nickel ultrafine particles produced thereby. More specifically, a raw material liquid containing an ultrafine particle component mainly composed of nickel ultrafine particles that can be used in electronic components is mixed with a solution containing the reducing agent and circulated in a reaction tube as a reaction liquid, A method and apparatus for producing ultrafine particles by irradiating at least a part of the reaction tube with microwaves, guiding the temperature of the reaction solution to the set temperature in a short time, and proceeding the reduction reaction of the raw material solution, and the production thereby Relates to fine nickel particles. The main aim of the ultrafine particles is 30 nm, but there are cases where the average particle diameter is 200 nm or less, 100 nm or less, 30 nm, or 10 nm or less depending on the purpose and application. Further, it may be in the form of a colloid or paste containing ultrafine particles.

  In recent years, research and development of nanoparticles having a particle size of 200 nm (nanometer) or less have been actively conducted, and many proposals have been made. For example, a reaction solution in which a solution containing a metal salt as a raw material for metal nanoparticles is mixed with a solution containing a reducing agent for the metal salt is circulated in a reaction tube, and microparticles are added to at least a part of the reaction tube. An example is an attempt to continuously produce metal nanoparticles by irradiating waves and heating the reaction solution in the reaction tube to a predetermined temperature suitable for the reduction reaction, thereby reducing the metal salt. is there.

  For example, a reaction solution containing silver nitrate as a metal salt and its reducing agent is circulated in a reaction tube made of glass or resin, and the reaction solution is irradiated with microwaves and heated, and the temperature of the reaction solution is suitable for the reduction reaction. It has been proposed to obtain a silver nanoparticle by increasing the temperature to a lower temperature and causing a reduction reaction of silver nitrate. However, if the reduction of the silver nitrate is continued, silver is deposited and attached to the inner wall of the reaction tube in a relatively short time. Since the silver adhering to the inner wall reflects the microwave, the microwave is not absorbed by the reaction solution, and the temperature of the reaction solution is rapidly lowered. As a result, there was a problem that a large amount of unreduced silver nitrate was mixed in the product, resulting in a low yield of silver nanoparticles. In addition, there were serious problems such as the inability to produce high-quality silver nanoparticles. However, there are not many patent literatures that discuss the above problems because there are not many examples of mass production of metal nanoparticles using microwave irradiation to reaction tubes.

  In many cases, the reduction reaction of a metal salt is performed not at room temperature but by heating to a temperature suitable for reduction of the metal salt and the reducing agent to synthesize ultrafine particles. And as a heating means, microwave irradiation may be used as a uniform and quick heating means.

  Many patent documents describe that irradiation of the reaction liquid with microwaves is expected to bring about a uniform and rapid rise in temperature of the reaction liquid, and the reduction reaction can be effectively advanced. And it is described that the variation in the particle size of the produced nanoparticles can be expected, the reaction time can be shortened, the production cost can be reduced, and the like.

  In the experiments by the inventors, a metal layer, a reducing agent, and a dispersing agent are poured into a reaction tube, and the reduction reaction is promoted under heating by microwave irradiation to produce metal nanoparticles. Has been confirmed to adhere to the inner wall of the reaction tube. In particular, in the case of silver nanoparticles, the level is serious. When precipitation of metal nanoparticles occurs on the wall surface of the reaction tube, the deposition layer generated on the wall surface of the reaction tube reflects the microwave. As a result, it has been confirmed that problems such as damage to the oscillator, the reaction tube, etc., heating of the reaction liquid with high uniformity, and no heating effect occur. This problem is also a serious problem in cases other than silver, such as copper and nickel.

  Further, in the experiments by the present inventors, it has been confirmed that there is a problem in the heating effect by the microwave when the metal nanoparticles are continuously produced while flowing the reaction liquid through the reaction tube. In addition, the reaction tube becomes clogged and the reaction solution does not flow, which may cause an explosion, cause a significant deterioration in the production quality of the metal nanoparticles, and the reaction tube must be replaced. It has been confirmed that a major problem occurs such as an increase in manufacturing cost. Moreover, it has been confirmed that the problem that the advantage of microwave irradiation is greatly impaired.

  However, a proposal has been made to solve the above-mentioned problem that occurs when producing nanoparticles while irradiating microwaves, but it is not sufficiently effective. When batch reaction is performed to irradiate the reaction solution with microwaves to reduce the metal salt in the reaction solution, metal deposits may adhere to the inner wall of the vessel and damage the vessel. Patent Document 1 describes a method for solving the problem.

  Patent Document 1 describes that a metal oxide or metal hydroxide dissolved in an organic solvent is reduced in a glass container to generate metal nanoparticles. Further, it is described that when the temperature of the reaction solution is increased using microwaves and the reduction reaction is continued for a certain period of time, metal fine particles adhere to the inner wall surface of the container. Further, it has been pointed out that the adhering matter is heated by absorbing microwaves, the container is locally heated, and the glass is broken.

  In order to solve this problem, in Patent Document 1, a mixed solvent of an organic solvent that easily absorbs microwaves and an organic solvent that hardly absorbs microwaves is placed in a 1 L (1 liter) separable container, and metal oxide is added to the mixed solvent. An organic modifier of equimolar amount or less is added to the product or metal hydroxide and metal element, and a reducing agent is added to the resulting solution to obtain a reaction solution, which is irradiated with microwaves from the outside of the container. It describes that metal nanoparticles are produced by heating a reaction solution. One of the reasons for using a mixed solvent of an organic solvent that easily absorbs microwaves and an organic solvent that hardly absorbs microwaves is close to the wall of the container when the reaction liquid is irradiated from the outside of the container. By the way, a mitigation measure against microwave absorption is given. Many types of metal salts, solvents that easily absorb microwaves, solvents that hardly absorb microwaves, and organic modifiers have been proposed.

  In Patent Document 1, a microwave transmitting material is further used for a portion where the metal fine particles of the reaction vessel are not deposited and adhered, and a microwave shielding member is disposed on a portion of the reaction vessel where the metal fine particles are deposited and adhered. Is described.

  According to the experiments of the present inventors, a reaction liquid is circulated through a tubular reaction tube made of a fluororesin part of which passes through a microwave irradiation field, the reaction liquid is irradiated with microwaves, and metal ions are reduced. In the case of producing metal nanoparticles, it has been found that deposits on the inner wall of the reaction tube cannot be avoided by conventional methods including Patent Document 1. It was also found that there were very serious problems.

For example, the reaction solution is circulated through a fluororesin reaction tube having an inner diameter of 2 mm, an outer diameter of 3 mm, and a length of a portion to be inserted into a cylindrical microwave cavity of 100 mm. Furthermore, microwave irradiation of the _{TM 010} mode frequency 2.4~2.5GHz in the reaction tube, to produce the copper nanoparticles, silver nanoparticles. In such a case, it is obvious that the method disclosed in Patent Document 1 cannot be used.

  In the reaction tube passing through the microwave cavity, a reaction liquid containing a metal nanoparticle and a metal nanoparticle dispersing agent synthesized with a metal salt and a reducing agent is flowed, and the reaction liquid is heated by irradiating microwaves with the metal. In the case of continuously producing nanoparticles, for example, when a metal salt is made into a silver salt, a silver precipitate is formed on the inner wall of the reaction tube. Moreover, reflection of the microwave occurs thereby. As a result, the microwave does not reach the reaction solution, and the temperature of the reaction solution, which has been the appropriate temperature for the reduction, is lowered to a temperature inappropriate for the reduction, and the unreacted metal salt is mixed in the product. As a result, the yield of nanoparticles becomes low.

  As described above, a reaction solution containing a silver salt dissolved solution, a silver nanoparticle dispersing agent, and a silver salt reducing agent is circulated in a reaction tube, and the reaction solution is irradiated with microwaves. When the temperature is raised to a suitable temperature for reduction and the reduction reaction is carried out, silver deposits begin to adhere to the inner wall of the reaction tube and various problems occur.

  That is, the microwave irradiated to the reaction tube from the outside of the reaction tube is reflected by the silver deposit attached to the inner wall of the reaction tube, so that the temperature of the reaction solution that has become the appropriate temperature for the reduction is made inappropriate for the reduction. It will decrease. Moreover, the unreacted solution is mixed in a predetermined amount or more, and the quality of the silver nanoparticles to be manufactured is deteriorated. A major obstacle occurs in the production of metal nanoparticles. Problems such as a large change in the temperature distribution of the reaction tube occur.

  Although such a phenomenon varies considerably depending on the type of metal to be manufactured, it is a problem to be solved that requires attention even for metals other than silver. For example, it has been confirmed that the above phenomenon also occurs in copper, nickel and the like.

  Continuous synthesis of various metal nanoparticles has begun to be proposed by published patents, and the possibility of productivity, simplicity, low cost, scale-up, etc. has been disclosed for the synthesis / purification method. However, no proposal has been made to actually solve the above problem.

  Although it has been quite a long time since the synthesis of nanoparticles was proposed, there are still many things that are unclear and must be resolved for commercialization. One example is the relationship between the particle size and physical properties of the nanoparticles.

  Although nickel nanoparticles are expected to be used in various applications such as internal electrodes of multilayer capacitors, bonding materials, and electromagnetic shielding materials, there is no established synthesis method for the synthesis of nickel ultrafine particles having a particle diameter of 300 nm or less. Currently. This is due to the difficulty in the synthesis reaction of nickel nanoparticles.

  In Patent Document 2, fine nickel particles are obtained, but silver ions are mixed into a raw material to function as a catalyst and a seed to form particles. Although it is a reduction by microwave irradiation, it is a reduction by an amine, so that nickel particles having an average particle diameter of 40 to 90 nm are obtained by reaction at 200 ° C. or higher.

  In Patent Document 3, nickel particles aggregated in a spherical shape of 25 nm to 30 nm are obtained, but ethyl acetate or toluene, which is a dangerous and highly harmful organic solvent, is used as a dispersion medium.

  In Patent Document 4, although nickel particles of 28 nm are obtained, Rongalite, which is a sodium salt of a reducing agent, is used.

  In Patent Document 5, nickel particles of 50 nm are obtained, but nickel chloride or sodium hydroxide is used. It is very expensive to completely remove impurities such as alkali metals and chlorine.

JP 2011-012290 A Japanese Unexamined Patent Publication No. 2013-7070 JP 2004-124237 A JP 2007-284715 A JP-A-2015-194415

  When nickel nanoparticles are used as a material for wiring by ink jet or the like, when forming a coating film, or when used for bonding, the particles should be 100 nm or less, or a hydrophilic alcohol-based dispersion medium. There is a need for colloids with good dispersibility.

When a metal is used for the material of the wiring or electrode, ion migration may occur if impurities such as alkali metal such as sodium or potassium, or chlorine exist in the metal. Silver is the most prone to ion migration, and the ease of occurrence depends on the metal species, and there is data that nickel is the speed of 10 ⁻³ of silver. However, since electronic components are miniaturized and miniaturized, nickel nano It is desirable that the particles do not contain such impurities.

  The problem to be solved by the present invention is to provide a metal ultrafine particle colloid, a paste manufacturing method, a manufacturing apparatus, a metal ultrafine particle colloid, and a paste that can provide ultrafine metal particles that solve the needs of the above market at an industrial level. There is to do.

  The problem to be solved by the present invention is, in particular, a nickel ultrafine particle colloid, a paste manufacturing method, a manufacturing apparatus, a nickel ultrafine particle colloid, and a paste that can provide nickel ultrafine particles that solve the needs of the above market at an industrial level. Is to provide.

  A first invention of the present invention (hereinafter referred to as Invention 1) made to solve the problem is to add an amine having an acid dissociation constant of 13 or more to a nickel-hydrazine complex formed from a nickel precursor solution and a hydrazine compound. In this way, a nickel ultrahydroid colloid production method is characterized in that an aqueous solution in which a hydroxide of a nickel-hydrazine complex is formed is continuously irradiated with microwaves and heated.

  According to a second invention of the present invention (hereinafter referred to as invention 2) made by developing the invention 1, the amine having an acid dissociation constant of 13 or more is 1,1,3,3-tetramethylguanidine. The method for producing a nickel-based ultrafine particle colloid as described in 1. above.

  A third invention of the present invention (hereinafter referred to as invention 3) made by developing inventions 1 and 2 is characterized in that single nanoparticles of nickel are added to a reaction solution. This is a method for producing a nickel ultrafine particle colloid.

  The fourth invention of the present invention (hereinafter referred to as Invention 4) made by developing Inventions 1 to 3 is characterized in that microwave heating is performed under pressure at a reaction temperature of 90 ° C. or more and 170 ° C. or less. The method for producing a nickel ultrafine particle colloid according to any one of inventions 1 to 3.

  The fifth invention of the present invention (hereinafter referred to as Invention 5) made by developing Inventions 1 to 4 is characterized in that a polyol is added to the reaction solution, according to any one of Inventions 1 to 4. This is a method for producing a nickel ultrafine particle colloid.

  A sixth invention of the present invention (hereinafter referred to as invention 6) made by developing inventions 1 to 5 is characterized by using a dispersant soluble in water and hydrophilic alcohol. 6. The method for producing a nickel ultrafine particle colloid according to any one of 5.

  A seventh invention of the present invention (referred to as Invention 7) made by developing Inventions 1 to 6 is an alkali metal, chlorine obtained by the method for producing a nickel colloid solution according to any one of Inventions 1 to 6. This is a nickel ultrafine particle colloidal solution which is dispersed in hydrophilic alcohol or water, which does not contain water.

  An eighth invention of the present invention (hereinafter referred to as Invention 8) made to solve the problem is to add an amine having an acid dissociation constant of 13 or more to a nickel-hydrazine complex formed from a nickel precursor solution and a hydrazine compound. In this way, the nickel ultrahydride paste manufacturing method is characterized in that the aqueous solution in which the hydroxide of the nickel-hydrazine complex is formed is continuously irradiated with microwaves and heated.

  According to a ninth invention of the present invention (hereinafter referred to as invention 9) made by developing the invention 8, the amine having the acid dissociation constant of 13 or more is 1,1,3,3-tetramethylguanidine. The manufacturing method of the nickel superfine particle paste as described in 1 above.

  The tenth invention of the present invention (hereinafter referred to as invention 10) made by developing the invention 8 or 9 is characterized in that nickel single nanoparticles are added to the reaction solution. This is a method for producing a nickel ultrafine particle paste.

  The eleventh invention of the present invention (hereinafter referred to as invention 11) made by developing the inventions 8 to 10 is characterized in that microwave heating is performed under pressure at a reaction temperature of 90 ° C. or higher and 170 ° C. or lower. The method for producing a nickel ultrafine particle paste according to any one of Inventions 8 to 10.

  The twelfth invention of the present invention (hereinafter referred to as invention 12) made by developing the inventions 8 to 11 is characterized in that a polyol is added to the reaction solution, according to any one of inventions 8 to 11. This is a method for producing a nickel ultrafine particle paste.

  A thirteenth invention of the present invention (hereinafter referred to as invention 13) made by developing the inventions 8 to 12 is characterized by using a dispersant soluble in water and a hydrophilic alcohol. 12. The method for producing a nickel ultrafine particle paste according to any one of items 12 to 12.

  The fourteenth invention of the present invention (referred to as invention 14) made by developing the inventions 8 to 13 includes an alkali metal and chlorine obtained by the method for producing a nickel paste according to any one of the inventions 8 to 13. It is a nickel ultrafine particle paste dispersed in hydrophilic alcohol or water that does not contain.

  When metal nanoparticles are used for electronic parts such as wiring, it is required that they do not contain impurities that may promote ion migration or deterioration. The nickel colloid of the present invention contains alkali metals and chlorine. It can be suitably used because it is not present. Moreover, since it is a synthesis | combination by 90 to 170 degrees C or less by a continuous method, it is excellent in energy cost and manufacturing cost becomes low. Furthermore, since it is a colloid dispersed in a hydrophilic alcohol-based dispersion medium without using a harmful organic solvent, it is environmentally friendly.

It is a schematic diagram of the nickel nanoparticle manufacturing apparatus used in the embodiment of the present invention. It is a schematic diagram of the nickel nanoparticle manufacturing apparatus used in another embodiment of the present invention. It is a figure which shows the temperature change of the reaction liquid by the microwave irradiation in the synthesis | combination of the nickel ultrafine particle as an Example of this invention. It is a figure which shows the reflected wave intensity change of the microwave by the microwave irradiation in the synthesis | combination of the nickel ultrafine particle as an Example of this invention.

1: Microwave irradiation port 2, 2a: Microwave irradiation field 4: Electric field monitor 5: Thermometer 6: Microwave oscillator / controller 7, 7a to 7n, 7r: Reaction tube 8: Reaction liquid 21, 21a to 21c: Gas source 22-25: T-shaped joint 30: Connection part 30a-30e: Reaction liquid extraction part 31, 32, 33, 33a-33c: Liquid source 34, 34a, 34c, x: Collection tank 71a-71c, 72- 78, 78a to 78c: flow paths a-1 to a-30: arrows S-1 to S-14: sensors 101, 101a, 101b, 101c: temperature curves 102, 102a, 102b, 102c: reflected wave intensity of microwaves curve

  Hereinafter, embodiments of the present invention will be described. In addition, in order to avoid duplication of explanation, the explanation of the nanoparticle production apparatus may also serve as explanation of the production method and nanoparticle, and vice versa. In addition, for convenience of explanation of the examples of the present invention, the drawings used for explanation of the embodiments of the present invention may be illustrated by partially changing the enlargement ratio without particular notice. And may not be similar to the description. Moreover, in each figure, the same code | symbol is shown about the same structural component, and duplication of description may be avoided.

  FIG. 1 is a schematic diagram of a nanoparticle production apparatus created to explain an embodiment of the present invention in consideration of various requirements. In the figure, not all the structural requirements are used for all the form examples, and some form examples are not necessary and may not be provided. To do. In FIG. 1, reference numeral 1 is a microwave irradiation port (waveguide, etc.), 2 is a microwave irradiation field, 4 is an electric field monitor, 5 is a thermometer, 6 is a microwave oscillator / controller, and 7, 7a and 7b are Reaction tube, 8 is a reaction liquid, 21 is an inert gas source, 22 to 25 are T-shaped joints, 30 is a connection part, 31 is a first liquid source (for example, A liquid, C liquid, etc.), 32 is a second Liquid source (for example, B liquid, D liquid, etc.), 33 is a third liquid source (for example, E liquid, etc.), 34 is a recovery tank, 72 to 78 are each liquid flow path or liquid and gas mixture flow path, Reference numeral 71 denotes an inert gas flow path. Of these, it is not necessary to provide all of them in the nanoparticle production apparatus, and the apparatus can be configured using only necessary ones. Reference numerals S-1 to S-14 are sensors for measuring information about the reaction solution such as temperature, pressure, flow rate, flow rate, electric field strength, etc. used for reaction system control and other purposes. Liquid source, liquid channel, gas channel , Placed in a collection tank, microwave irradiation field, etc. The sensor may not be provided if unnecessary. a-1 to a-9 are arrows. The liquid feed pump is not shown. Some embodiments may be configured with only a portion of the illustration. Although not shown, a stirring device is arranged in each liquid source, a recovery tank, etc., to make each liquid, reaction liquid, etc. uniform.

  In FIG. 1, for example, a case where at least reference numerals 33 and 24 are not provided will be described. For example, when there are two kinds of liquids to be mixed, the first kind of liquid is prepared in the liquid source 31, the second kind of liquid is prepared in the liquid source 32, and a plunger as a liquid delivery means is provided in each liquid source, for example. A pump is provided and set to each predetermined liquid feeding speed. The liquids from the liquid sources 31 and 32 are sent from the liquid sources 31 and 32 through the liquid flow paths 73 and 74 in the directions of arrows a-2 and a-7, respectively, at predetermined speeds. Then, the inert gas sent from the inert gas source 21 in the directions of arrows a-1 and a-4 is introduced. Thereafter, each liquid into which the inert gas has been introduced passes through the flow paths 77 and 76, is sent to the T-shaped joint 25, is mixed by the T-shaped joint 25, and is discharged from the remaining flow paths of the T-shaped joint 25. One end is sent to the liquid flow path 78 connected to the reaction tube 7.

  1, the liquid in the liquid stock 33 passes through the liquid flow path 72 at a predetermined speed, and after the inert gas from the inert gas source 21 is introduced by the T-shaped joint 24, The T-shaped joint 23 is mixed with the liquid from the second liquid source 32. At this time, the inert gas from the inert gas source 21 is also mixed with the liquid from the second liquid source 32. Note that the inert gas source 21 may be directly disposed in the second liquid source 32 depending on the type of liquid.

  The liquid from the liquid flow path 78 enters the reaction tube 7 passing through the cavity 2 as a microwave irradiation field, and receives microwave irradiation in the microwave irradiation field 2.

  The optimum shape of the reaction tube 7 in the microwave irradiation field 2 may vary depending on the microwave frequency, the microwave mode, the type of liquid, etc. within the range of 300 MHz to 300 GHz. By appropriately selecting the shape of the reaction tube 7 in the microwave irradiation field 2, the effect of the microwave irradiation can be controlled.

  Examples of the shape of the reaction tube 7 include a linear shape, an S-shape, a coil shape, and a mixed shape thereof. Moreover, the effect of microwave irradiation can be controlled by disposing a part of the reaction tube 7 outside the microwave irradiation field 2.

  The connection part 30 is a connection part that connects the output part 7a of the reaction tube 7 and the reaction tube 7b, and may not be provided depending on the purpose of manufacturing the nanoparticles, the state of the apparatus, and the parts. In that case, the reaction tube 7b may have the same specifications as the reaction tube 7, or the diameter may be changed depending on the purpose. Reference numeral 30a denotes a reaction liquid take-out portion, which is provided as necessary and may be used for reaction control. It should be noted that the outer diameter and inner diameter of the reaction tube can be changed even in a portion not shown depending on the configuration of the apparatus.

  In the reaction liquid take-out section, the reaction state judgment means for fine particles, particle diameter observation means, particle diameter distribution observation means, component observation means, particle size selection and classification means such as ultrafiltration, classification means, flow dividing means, heating and It is preferable to provide at least one of temperature adjusting means including cooling as required. For example, when reaction state determination means (not shown) is arranged in the reaction liquid extraction unit 30a, a reaction liquid having a predetermined level or less is extracted, and the nanoparticles used in other embodiments of the present invention are used. As will be described later with reference to FIG. 2, which is a schematic diagram of the manufacturing apparatus of FIG.

  As a result of various examinations of the embodiments of the present invention, in order to prevent deposits from being deposited on the inner wall of the reaction tube in the synthesis process including the reduction reaction of the nanoparticle raw material liquid after receiving microwave irradiation, It has been found preferable to introduce an inert gas into the reaction solution before irradiation. It has also been found that the introduction of the inert gas has important factors such as how each liquid constituting the reaction liquid is circulated and how the inert gas is introduced. Even if an inert gas is introduced into the reaction liquid after the first liquid and the second liquid are mixed to form a reaction liquid, the occurrence of a mirror phenomenon on the reaction tube wall can be alleviated. In addition, a method of introducing an inert gas into the first liquid, a method of introducing an inert gas into the second liquid, or an inert gas is introduced into the second liquid and allowed to flow through the liquid flow path. The method of mixing the first liquid into the place where the first liquid is introduced, and the method of mixing the first liquid into which the inert gas is introduced into the place where the inert gas is introduced into the second liquid and circulated in the liquid flow path For example, there are appropriate methods according to the method of selecting the raw material of the nano particles and the reducing agent.

  By flowing the reaction liquid into which the inert gas has been introduced into the reaction tube, it is possible to effectively prevent metal deposits from adhering to the inner wall of the reaction tube. For example, when synthesizing metal nanoparticles, the first liquid containing the metal salt into which the inert gas is introduced is mixed with the second liquid containing the reducing agent into which the inert gas has been introduced. And a method of mixing the first liquid containing the metal salt into the place where the second liquid containing the reducing agent introduced with the inert gas is circulated in the pipe. Even when the first liquid and the second liquid are mixed to form a reaction liquid and then an inert gas is introduced into the reaction liquid in the next stage, the remarkable effect of introducing the inert gas can be exhibited. .

  For example, the liquid from the first liquid source and the liquid from the second liquid source are allowed to flow through the flow path, respectively, and an inert gas is mixed with each liquid, and both liquids are mixed with a T-shaped joint to form a reaction liquid. Then, an embodiment of a method for irradiating the reaction solution with microwaves will be described.

  The measurement results of the electric field monitor 4 and the thermometer 5 shown in FIG. 1 are first fed back to the microwave oscillator / controller 6. The flow rate of the inert gas is measured by the sensors S-8 and S-1 in FIG. Sensors S-1 to S-13 indicate the flow rate, flow rate, and components of each liquid, gas, and mixture constituting the reaction liquid; the state of the particle size / distribution of the nanoparticles; and the mixed state of the reaction liquid and the gas. Measured as necessary, sent to microwave oscillator / controller, each liquid feeding device, temperature control device (not shown), control system controlling nanoparticle synthesis system in some cases, synthesis quality of nanoparticles Can be managed.

  Optical and / or electrical detection means for depositing deposits on the inner wall of the reaction tube can be provided in the reaction tube, control circuit, and the like. Electrical and / or optical measuring means such as the reaction process of the reaction solution, the particle size and particle size distribution of the nanoparticles after the reaction, and the average particle size can be provided in the reaction tube or the vicinity thereof or in the recovery tank.

  In the embodiment of the present invention, the state of metal deposit adhesion to the inner wall of the reaction tube is judged by measuring the temperature of the reaction solution and the electric field strength of the reflected wave of the microwave, and the result is synthesized with the nanoparticles. Used for control. Moreover, information from each sensor is also used for nanoparticle synthesis control as necessary.

  In the experiment of the present invention, as an example of a reaction tube, a reaction tube made of a fluororesin that transmits microwaves at least to a portion irradiated with microwaves was used as a basic portion. However, the scope of rights of the present invention is not limited to this reaction tube. As the reaction solution, first select a material that easily deposits precipitates on the inner wall of the reaction tube, such as copper or silver, that is, a material containing a component that easily forms a copper mirror, silver mirror, nickel mirror, etc. on the inner wall of the tube. And a reaction solution containing a reducing agent was prepared. The reaction solution was circulated in the reaction tube. While irradiating the reaction liquid in the reaction tube with microwaves in at least a part of the reaction liquid channel, the reduction reaction proceeds to a predetermined temperature suitable for the reduction of the reaction liquid, and deposits are generated on the inner wall of the reaction tube It was investigated variously.

  The microwave used for heating the reaction solution can be either single mode or multimode. The microwave resonator may be either a cylindrical type or a rectangular type, but a cylindrical type is more preferable. In general, a microwave is sent from a magnetron, a semiconductor oscillator, or the like to a microwave irradiation field for heating a sample through a waveguide. Also, depending on the microwave mode, a microwave reflector may be provided at one end of the waveguide to reflect it, and a mode that concentrates the electric and magnetic fields at a specific position in the waveguide may be formed to generate heat in the sample. it can.

As the microwave frequency band, a 2.4 to 2.5 GHz band frequency was used from the viewpoint of availability of the apparatus, and experiments were also performed at frequencies other than those described above. As the microwave mode, a _TM010 mode was mainly used as a single mode. However, the microwave frequency and mode are not limited to this.

When the TM mode is used as the _microwave mode, it is particularly preferable to use the TM _mn0 mode where m is an integer of 0 or more and n is an integer of 1 or more. When the TE mode is used, it is particularly preferable to use the TE ₀₁₁ , TE ₁₀₁ , TE ₀₁₂ , and TE ₂₀₁ modes.

  Not only single mode but multi mode can be used. Microwave irradiation is not limited to a cylindrical microwave resonator, and any device that can use the advantages of microwave heating, such as one using a rectangular waveguide, can exhibit the effects of the present invention.

In the embodiment, a cylindrical microwave resonator having a maximum microwave output of 500 W was used as the resonator, and PFA was used as a material for the reaction tube. As the microwave mode, _TM010 of single mode which is one of the modes excellent in accuracy is used. Note that the scope of the present invention is not limited to these.

The dimensions of the basic part of the reaction tube are not limited to this, but a basic part having an outer diameter of 3 mm, an inner diameter of 2 mm, and a basic part entering the microwave resonator of 41 cm was used. In the reaction tube, 10 cm out of the length of 41 cm of the basic portion is arranged in the central portion of the microwave cavity in a direction substantially perpendicular to the _TM010 mode of microwaves, and the microwave is added to the reaction liquid flowing through the reaction tube. Was applied to effectively heat the reaction solution to a predetermined temperature to proceed the reduction reaction. A reaction tube having the same inner diameter was connected before and after the basic portion of the reaction tube in the flow direction of the reaction solution, which was used as an input side and an output side of the reaction solution, respectively.

  As a result of various investigations on the flow of inert gas, when metal nanoparticles are synthesized by reducing metal nanoparticles with the reducing agent, the optimum inert gas depends on the type of metal nanoparticle precursor and the type of reducing agent. It was found that there was a difference in the way of introduction of the active gas into the reaction liquid and the timing of introduction. In the reduction reaction of metal nanoparticles, when the mirror reaction is relatively intense, for example, when the metal element is silver and dimethylaminoethanol is used as the reducing agent, an inert gas is introduced into the solution containing the silver nanoparticle reducing agent. It was found that it was possible to more effectively prevent the metal deposits from adhering to the inner wall of the reaction tube by mixing the raw material solution of the metal nanoparticles therein. In addition, when the metal element is copper and hydrazine is used as the reducing agent, a liquid containing copper ions and a liquid containing hydrazine are mixed to form a reaction liquid, which is then flowed into the reaction tube, immediately before the microwave irradiation field. It was found that it is preferable to introduce an inert gas into the reaction solution.

  The temperature in the microwave irradiation field is likely to fluctuate even if the temperature is controlled because the reaction solution flows in the reaction tube while carrying out a reduction reaction with an inert gas inserted. However, as a result of investigation during the synthesis of silver nanoparticles, it was found that there was little sudden drop in temperature, and the maximum temperature drop was 15 ° C. It has also been found that suppressing this temperature drop to 10 ° C. or lower can promote continuous production of nanoparticles more stably. The temperature change of the reaction solution was measured every second. The instantaneous temperature drop refers to a peak value when the pulse temperature fluctuates from the set temperature. In other words, the “abrupt instantaneous decrease in temperature” refers to a decrease in a pulse-like decrease from the set temperature when the temperature in the microwave irradiation field is measured every second. Further, in the present invention, it is preferable that “sudden momentary temperature drop” is 15 ° C., preferably 10 ° C. or less.

  With regard to the synthesis of silver nanoparticles, in the configuration shown in FIG. 1, a liquid containing silver nitrate as a first liquid is used as a first liquid source, and a liquid containing a silver nitrate reducing agent is used as a second liquid as a second liquid. Prepare to the liquid source, each with a plunger pump at each predetermined liquid feed speed, sent to the T-shaped joint through each liquid flow path, and when both liquids are mixed with the T-shaped joint, the temperature rises to a suitable temperature for reduction. The two liquids mixed before the start of the reduction started to reduce, and it was observed that the reaction liquid flowing through the liquid flow path connected to the T-shaped joint changed from transparent to black.

  In order to insert nitrogen gas at an early stage, the length of the liquid flow path through which the reaction liquid flows is about 3 cm, and the end of the liquid flow path opposite to the end connected to the T-shaped joint is the second. Liquid connected to one end of the second T-shaped joint together with the reaction liquid by inserting nitrogen gas from the flow path connected to one end of the second T-shaped joint. It was made to flow into the reaction tube passing through the flow path and passing through the microwave irradiation field. Thereby, the synthesis | combination of the silver nanoparticle was able to be performed over a long time, without producing deposit adherence on the inner wall of the reaction tube.

  In addition, the temperature of at least a part other than the part passing through the microwave irradiation field of the reaction tube is controlled by using temperature control means other than the microwave as a heating source or a cooling source to control the particle size of the metal nanoparticles. be able to. Although not limited to this, for example, the above-mentioned part is brought into contact with a relatively good heat conductive object provided with a Peltier element, passed through such a container, or the first and second liquid sources. It is possible to control the particle size of the metal nanoparticles by controlling the temperature of at least one of them using a Peltier element.

  Since the Peltier element can be used for both raising and lowering the temperature by electrical control, the particle size control, reaction suitability temperature, and particle size control temperature of the metal nanoparticles can be controlled appropriately.

  In addition, at least part of the first liquid, the second liquid, the gas, the flow path of the reaction liquid, or the vicinity thereof in the manufacturing process of the metal nanoparticles, the reaction progress information about the temperature, the flow rate, the liquid, A sensor that detects at least one of the information regarding the particle diameter can be arranged, and the output can be fed back to a predetermined control system for control.

  In addition, means for measuring the particle size of the metal nanoparticles in the flow path or shunt of the reaction solution in the continuous production process of metal nanoparticles can be provided, and the particle size of the metal nanoparticles at that time can be measured.

A T-type or Y-type joint is provided in the flow path or shunt of the reaction liquid, and the reaction liquid is collected from the joint to measure the particle size of the metal nanoparticles, or the metal in the flow path or shunt of the reaction liquid A means for directly measuring the particle diameter of the nanoparticles, for example, a measuring means using phase rotation of laser light can be provided.
The information on the particle size, the temperature control information, and the flow rate control information are useful for controlling the particle size distribution of the metal nanoparticles to be synthesized, for example.

  As a result of examining the flow rate of nitrogen gas, even a slight amount helps to reduce the mirror phenomenon. However, in the case of the above-mentioned fluororesin reaction tube having an inner diameter of 2 mm and a microwave irradiation region of 100 mm, when the reaction solution is silver, 0. The effect of flowing nitrogen gas into the reaction solution at 4 L / min or more is great. It has been found that controlling the total flow rate suitable for mass production to 0.5 L / min or more, more preferably 1 L / min or more shows a stable effect. The total flow rate is more preferably 2 L / min or less.

The total insertion amount of the inert gas into the reaction liquid when the average inner diameter of the reaction tube for flowing the reaction liquid is 2 r (mm) is preferably 0.4 × r ² (liter) / min or more. More preferably, it is 0.5 × r ² (liter) / min or more, and further preferably 1.0 × r ² / min or more. However, economically, it is desirable not to exceed 3.0 × r ² (liter) / min.

  The linear velocity of the inert gas inserted into the reaction solution in the reaction tube is preferably 2 m / sec or more. When the linear velocity is 5 m / sec or more, stable synthesis can be continued.

  Furthermore, as a result of experimenting with various types of gases as the inert gas, it was found that an inert gas other than nitrogen, such as argon, has the same effect. However, nitrogen gas is particularly preferred economically.

  Further, before mixing the first liquid and the second liquid into a reaction liquid, a gas is inserted into at least one of the first liquid and the second liquid to form a multiphase flow, and then the first liquid and the second liquid are mixed. By mixing the first liquid and the second liquid into a reaction liquid, the reaction system can be precisely controlled.

  Before mixing the first liquid and the second liquid into a reaction liquid, different types of gases can be used as the gases inserted into the first liquid and the second liquid. In addition, after the first liquid and the second liquid are mixed, a step of inserting a gas is further provided, so that the quality of control can be adapted to the type of metal.

  Moreover, it is preferable to have the process of controlling the pressure or linear velocity of the gas to insert.

  Although examples using M-1000, PVP, tartaric acid derivatives, and Diperbyk-2015 have been described as the nanoparticle dispersant, the dispersant is preferably a hydrophilic one, for example, polyoxyalkyleneamine. There are many dispersants such as monoamines, diamines and polyacrylic acids. In addition, a magnetic stirrer was used to use the stirring action for adjusting the liquid constituting the reaction liquid, but the present invention is not limited to this, and other methods such as using ultrasonic waves can be used. It is. When using ultrasonic vibration, for example, low frequency ultrasonic waves such as 30 KHz, medium frequency ultrasonic waves such as 200 KHz, and relatively high frequency ultrasonic waves near 500 KHz are used. Thus, the effect of the present invention can be further increased.

  When the reaction solution is irradiated with microwaves, ultrasonic waves can be propagated, and thereby the particle diameter and distribution of the synthesized nanoparticles can be controlled.

  Examples of means for purifying the metal nanoparticle colloid include filtration with a filter and ultrafiltration.

  In the examples, the T-shaped joint is used for mixing the A liquid and the B liquid and the reaction liquid and the inert gas. However, the present invention is not limited to this, and the Y-shaped joint, By using a joint designed so that various types of liquids and gases can be mixed in consideration of the type and nature of the liquid and inert gas to be used, the effects of the reduction reaction and the like are precisely controlled. The effect can be further increased.

  Then, among the liquid containing the reducing agent of the metal nanoparticle precursor to be circulated in advance and the liquid containing the metal nanoparticle precursor to be mixed therewith, at least the liquid containing the reducing agent of the metal nanoparticle precursor is added to the metal nanoparticle precursor. More preferably, the gas is inserted before mixing the liquid containing the particle precursor. It has been found that when an inert gas is used as the gas, a particularly great effect is exhibited.

Moreover, although the example which uses _TM010 mode for the mode of the microwave used for reaction promotion of a reaction liquid was described as an Example, this invention is not limited to this narrowly. For example, a microwave standing wave of TM _mn0 mode (m is an integer of 0 or more and n is an integer of 1 or more) has a concentration of electrolysis in the radial direction of the cylinder, and a uniform electric field strength at a position parallel to the central axis. Are available as well.

  In microwave heating, heating by an electric field can be used, but heating by a magnetic field can also be used.

  In order to stabilize the synthesis of the nanoparticles, increase the synthesis possible time, and improve the synthesis quality, it is preferable to better control the flow of the reaction solution.

  As one of the means, there is a method in which various measuring means for monitoring the progress of the reaction of the reaction solution are installed in various places as described above. At least one of an electric field monitor for monitoring the electric field of the microwave and a thermometer for detecting the temperature in the microwave irradiation field or the temperature of the reaction tube is provided in the microwave irradiation field, and the measurement result is fed back to the microwave oscillator / controller. In addition to controlling the transmission status of microwaves, it is possible to construct a high-level automated manufacturing system.

  Although not shown, various measuring means can be provided everywhere as required. At least part of the electric field monitor and thermometer are fed back to the microwave oscillator / controller. In addition, with regard to the flow rate of the inert gas, for example, a means for measuring the flow rate per minute can be provided in a part of the flow path or the inert gas source, and the flow rate and components of each liquid constituting the reaction liquid can be determined. The measuring means can be provided in the T-shaped joint or the liquid flow path in front of it, the temperature measuring means is not limited to the thermometer, and it can be provided at a key point, and the optical deposit of deposits on the inner wall of the reaction tube And / or an electrical detection means can be provided in the reaction tube, the control circuit, etc., and the electrical and / or the reaction process of the reaction solution, the particle size and particle size distribution of the nanoparticles after the reaction, the average particle size, etc. Optical equal measuring means can be provided in the reaction tube or the vicinity thereof, or in the recovery tank.

  The reduction suitability temperature varies depending on the metal salt, the reducing agent, the dispersant and other additives.

  In the embodiment in the case of silver, the suitable temperature for reduction is 70 ° C., and therefore, the set temperature of the microwave was set to 70 ° C., and the reflected power and temperature were measured. In the case where no inert gas was introduced into the reaction solution, the reflected power in the 86 seconds from 54 seconds to 140 seconds after the reaction temperature reached 70 ° C. after starting the microwave irradiation was 75 to 308 W. Moreover, it was 46 times that recorded 150W or more in the meantime, and it was 2 times that exceeded 300W in the meantime. The reflected power during 152 seconds from 140 seconds to 292 seconds to be stopped was 38 to 503 W, 150 W or more was 78 times, and 300 W or more was 22 times. It was dangerous to continue any further, so microwave irradiation was stopped. On the other hand, in the case of the above-described embodiment in which an inert gas is introduced into the reaction solution, after the microwave irradiation is started, the reaction temperature reaches 70 ° C., 52 seconds after the experiment ends from 352 seconds. The reflected power in 300 seconds was 0 to 219W. In addition, 100 times or more was recorded 12 times during that time, of which 150 W or more was recorded 5 times, of which 200 to 230 W was recorded 2 times. Moreover, there was no 230W or more. From this, it can be said that a mirror can be easily formed at least when the number of times the reflected power is 150 W or more is 8 times or more in 20 seconds. The effect of liquid backflow must also be considered.

  The measurement results of these various measuring means can be controlled according to manufacturing specifications and the like. For example, the average particle size, particle size distribution, and the like can be controlled by feeding back measurement data to a microwave oscillator / controller and / or a system control circuit (not shown) to control the manufacturing system.

  Hereinafter, the present invention will be described in more detail with reference to FIG. 2 which is a schematic diagram of a nanoparticle production apparatus used in another embodiment of the present invention.

  The inventors introduced simulation software such as microwave irradiation, heat transfer status, and chemical reaction depending on the manufacturing conditions, and investigated the correspondence between the manufacturing conditions and the progress, manufacturing speed, manufacturing quality, and the like. As software, simulation software such as software for simulating microwave modes and overheating conditions, software for simulating heat transfer conditions and temporal changes, and software for simulating the state of chemical reactions was used. For example, the simulation is performed using a COMSOL MULTIPHYSICS RF module, a heat transfer module, a chemical reaction engineering module, a particle tracing module, a CFD module, an optimization module, and the like as appropriate. Then, we compared the simulation results with partial experiments and actual manufacturing processes, and considered them. Process management data was created by combining the results with actual experiments and manufacturing process parts or the whole. It was used for actual manufacturing management.

  In addition to a metal salt and a reducing agent, a reaction solution in which a dispersant, a surfactant, a protective material, a solvent and the like are mixed as necessary is prepared. It is irradiated with microwaves in a microwave irradiation field. The reaction liquid that promotes the reduction reaction is sent to the reaction liquid take-out section. In the case where reaction state judging means (not shown) is arranged in the reaction liquid take-out portion shown in FIG. 1 or 2 described later, a reaction tube that extracts a reaction liquid below a predetermined level and passes through the microwave irradiation field again. And irradiate with microwaves.

  The frequency of the microwave to be irradiated can be selected according to the reaction purpose. In many cases, 2.4 to 2.5 GHz, which is economically available, is preferable. However, depending on the purpose of the reaction process and the control conditions, for example, it is suitable for subtle adjustment of the heating rate, flow rate, reaction tube conditions, etc. We also studied using different frequencies.

  In FIG. 2, reference numeral 2 a is a microwave irradiation field, 7 a to 7 n and 7 r are reaction tubes, 21 a to 21 c are gas sources, 30 b to 30 e are reaction liquid outlets, 33 a to 33 c are liquid sources, and 34 a, 34 c and x are Collection tanks 71a to 71c and 78a to 78c are flow paths, and a-10 to a-30 are arrows.

  In the apparatus for producing fine particles such as nanoparticles of the present invention, particle size selection such as reaction state judgment means for fine particles, particle size observation means, particle size distribution observation means, component observation means, ultrafiltration, etc. is provided at a necessary portion such as a reaction liquid take-out part In addition, at least one of classification means, classification means, flow dividing means, temperature adjusting means including heating and cooling, and the like can be provided to improve the production quality of the fine particles to be produced.

  With reference to FIG. 2, the flow of the reaction liquid in the embodiment of the present invention will be described. The reaction solution that has advanced through the flow path 78 in FIG. 1 in the direction of arrow a-8, enters the reaction tube 7 and has been irradiated with microwaves proceeds through the reaction tube 7a in the direction of arrow a-9, and passes through the connection portion 30 to react. The pipe 7a is advanced in the direction of arrow a-10 and reaches the reaction liquid outlet 30a. The reaction liquid that has reached the reaction liquid extraction section 30a is subjected to a first predetermined standard and a second predetermined value by a reaction state determination means (not shown) and classification means (not shown) arranged in the reaction liquid extraction section 30a. It is classified as a standard. The reaction liquid classified into the first predetermined standard advances through the reaction tube 7b in the direction of arrow a-11 and is stored in the recovery tank 34. The reaction liquid classified into the second predetermined standard travels along the reaction tube 7c in the direction of arrow a-12 and reaches the reaction liquid extraction part 30b.

  The reaction solution that has reached the reaction solution extraction unit 30b is subjected to a third predetermined reaction in which the reaction is insufficient by a reaction state determination unit (not shown) or a classification unit (not shown) arranged in the reaction solution extraction unit 30b. The reaction liquid classified into the fourth predetermined standard having a large particle diameter and the fourth predetermined standard proceeds in the direction of arrow a-13, and is stored in the recovery tank 34a for a predetermined application. Alternatively, it is dissolved again and put into a reaction solution of the third predetermined standard.

  The reaction liquid of the third predetermined standard travels through the reaction tube 7d in the direction of arrow a-14 and reaches the reaction liquid outlet 30c. The reaction solution that has reached the reaction solution outlet 30c travels in the direction of the arrow a-17 through the reaction tube 7e, enters the reaction tube 7f, and receives microwave irradiation again. In the reaction liquid extraction unit 30c, a gas flowing from the gas source through the flow path 71a in the direction of the arrow a-15 is introduced into the liquid flowing from the liquid source 33a through the flow path 78a as necessary to obtain a reaction liquid.

  The reaction solution that has entered the reaction tube 7f and has been again irradiated with microwaves travels in the reaction tube 7g in the direction of arrow a-18 and reaches the reaction solution outlet 30d. In the reaction liquid extraction unit 30d, the reaction liquid classified into the fifth predetermined standard advances through the reaction tube 7n in the direction of arrow a-20 and is stored in the recovery tank 34b. Alternatively, when the reaction liquid is the same as the reaction liquid passing through the reaction tube 7a, the reaction flows through the reaction tube 7h in the direction of the arrow a-19 to reach the connection portion 30 and then flows through the reaction tube 7a in the direction of the arrow a-10. Become liquid. When the reaction solution is other than those, it flows through the reaction tube 7i in the direction of arrow a-21 and reaches the reaction solution extraction part 30e. In the reaction liquid extraction unit 30e, the liquid from the liquid source 33b flowing in the direction of the arrow a-23 in the flow path 78b and the gas from the gas source 21b flowing in the direction of the arrow a-22 in the flow path 71b are mixed. It flows through the flow path 78b in the direction of arrow a-24 and is mixed with the reaction solution from the reaction tube 7i. The mixed solution enters the reaction tube 7k from the reaction tube extraction portion 30e through the reaction tube 7j, receives microwave irradiation, flows through the reaction tube 7l in the direction of arrow a-26, and reaches the reaction solution extraction portion 30f. The microwave irradiation at this time may be performed under conditions different from those applied to the reaction tube 7. In this case, a microwave irradiation field different from the microwave irradiation field may be used.

In the reaction liquid extraction unit 30f, the liquid in the liquid source 33c mixed with the gas from the gas source 21c flowing in the flow path 71c in the direction of arrow a-27 flows in the flow path 78c in the direction of arrow a-28 under predetermined conditions. And mixed with the reaction solution from the reaction tube 7l. The mixed solution flows through the reaction tube 7m in the direction of the arrow a-29 and receives microwave irradiation in the microwave irradiation field 2a.

  The reaction solution that has been subjected to microwave irradiation in the microwave irradiation field 2a flows through the reaction tube 7r in the direction of arrow a-29 and enters the recovery tank x. In the recovery tank x, the reaction liquid can be subjected to physical, chemical, electrical or other synthesis or processing. For example, a synthetic substance can be formed or a device can be created.

  In FIG. 2, the sensors as shown in FIG. 1 are not shown in order to avoid the complexity of the figure, but various sensors are arranged where necessary, and the detection results are used to control the system and parts. It is reflected.

  One of the methods for producing nanoparticles with uniform particle size is to weaken the microwave irradiation conditions, lower the reactivity, classify using the reaction progress judgment means and classification means, etc. Controlling the particle size can be exemplified by selective repeated irradiation. As a means for selecting the particle size, for example, ultrafiltration can be used. In addition, modification of the nanoparticles is possible by using a reactive gas.

  In the microwave irradiation field, by providing means for changing the traveling direction of the microwave incident on the microwave irradiation field (microwave direction changing means), the conditions of the microwave irradiated to the reaction liquid can be changed.

  For example, the microwave direction changing means can change the traveling direction of the microwave by computer control based on detection data of a predetermined sensor. Detects the microwave absorption field and the microwave absorption status of the reaction solution after microwave irradiation, the change status of the reaction solution such as temperature, etc., and can control the manufacturing conditions appropriately in response to subtle changes in the reaction solution It is.

  In addition, the metal nanoparticles produced by the method of the present invention are highly likely to contain at least a trace amount of gas, inert gas, nitrogen gas and the like inserted into the reaction solution to form a mixed phase flow.

  The metal nanoparticle of the present invention can be a product taking the above-mentioned various forms according to the customer's request. The present invention is not limited to the various examples described above, and many variations are possible according to the technical idea of the present invention. For example, based on the detection information from the sensor of FIG. 1 or FIG. 2, depending on how to combine the components, whether to use or not, and depending on the nanoparticle, hydrogen with reducing power or reactive gas with substance modification Improvement of nanoparticles by use, cleaning of components, etc. can be mentioned. In addition, the present invention described with reference to FIG. 2 is a manufacturing process, a manufacturing apparatus, and nanoparticles manufactured using the reaction liquid in which the reaction liquid does not mix the gas from the gas source. The present invention can also be applied to the present invention, and exhibits a great effect that nanoparticles having a uniform particle size can be provided at low cost.

In the description of the present invention, the description has focused on introducing an inert gas as a gas into the reaction solution to prevent deposits from adhering to the inner wall of the reaction tube. Reducing hydrogen gas can be introduced instead of inert gas, reactive gas used in the semiconductor field, etc. can be introduced, preventing mirrors, imparting physical properties, and reforming It is also possible. It is also possible to provide a plurality of microwave irradiation portions and use them for multiple purposes under control, that is, to carry out reduction reactions and the like with high accuracy. It is also possible to use a plurality of types of wavelengths as the microwave.
Various measurements and processing can be performed in combination with the measuring device for the fine particles themselves.

  In the example of the present invention described below, a solution of a nickel complex containing a reducing agent is continuously heated to 170 ° C. or lower under pressure, taking advantage of the fact that microwaves can be rapidly and uniformly heated. Thus, in the method for producing a nickel colloid of 100 nm or less, the reduction is carried out by adding a polyol in the presence of a single nanoparticle nickel colloid and a dispersant soluble in water or hydrophilic alcohol. This is a method for producing a nickel colloid.

  The solution of the nickel complex containing the reducing agent mentioned above is a 1,1,3,3-tetramethylguanidine, 1,3,3-, in order to make the reducing agent hydrazine, solubilize in water, and perform the reaction quickly. An amine having a pKa of 13 or more such as diphenylguanidine is added as an alkali to form a hydroxide of a nickel-hydrazine complex.

  The acid dissociation constant of 1,1,3,3-tetramethylguanidine was 13.6, and 1,3-diphenylguanidine was 14.5, which was found to be sufficient for reducing nickel ions. It was also found that 1,1,3,3-tetramethylguanidine can be made water-soluble by making nickel hydrazine complex a hydroxide. An amine having an acid dissociation constant of 13 or more may be used alone or in combination.

  Furthermore, alkanolamine or amine can be added in addition to 1,1,3,3-tetramethylguanidine in order to increase the pH and increase the reaction rate. Although not limited, ethanolamine having a boiling point as high as 170 ° C. is preferable.

  Nickel acetate is preferred as the nickel precursor for preparing the nickel complex solution containing the reducing agent, and nickel formate, nickel oxalate, nickel nitrate, and nickel chloride are insufficient. In order to obtain a nickel colloid of 100 nm or less without the presence of coarse particles, it is important to reduce the nickel complex to a solution state.

  By filtering the solution of the nickel complex containing the reducing agent, excess hydrazine can be separated and a reduction reaction can be performed. In that case, when it does not become an aqueous solution only by adding 1,1,3,3-tetramethylguanidine, an alkanolamine can be added to make an aqueous solution.

  The method for producing a nickel colloid according to the present invention is to continuously reduce by heating by microwave irradiation under pressure.

  The pressurization is for increasing the reaction temperature to increase the reaction rate and to produce nickel particles of 100 nm or less. It was found that when the reaction was carried out at 90 ° C. or lower without applying pressure, a large number of nickel particles of 200 nm or more were produced.

  The pressurization is not limited, but 0.1 to 0.5 MPa is effective from the viewpoint of safety.

  In the continuous reduction, a gas such as nitrogen gas can be passed through the reaction tube. When metal is produced by reduction, metal deposits in the reaction tube, absorbs microwaves and cannot be heated, and eventually sparks, but is deposited by flowing gas through the reaction tube. Can be prevented. Although the kind of gas is not ask | required, nitrogen gas is suitable and it is preferable that the flow volume flows the flow volume which makes the flow of a reaction liquid constant.

  In the continuous reduction, ultrasonic waves can be irradiated by passing the reaction tube through the ultrasonic device before the reaction tube enters the cavity of the microwave device. Specifically, in FIG. 1, when a nickel-hydrazine complex hydroxide solution is introduced into a liquid source 32 and is allowed to flow, an ultrasonic device can be provided in the flow path 74 or the flow path 76.

  By irradiating the liquid with ultrasonic waves before heating by microwave irradiation, the particle diameter of the produced nickel can be made fine.

  The frequency of the microwave device can be 2450 MHz, for example, and it is preferable to use a single-mode microwave device that controls the frequency.

  The method for producing a nickel colloid according to the present invention is to microwave heat a liquid containing nickel particles of single nanoparticles.

  It was found that by adding nickel of the single nanoparticle, the reduction temperature of the nickel complex can be lowered, and nickel particles having a small particle size can be generated. In the prior literature, noble metal ions are added to the reaction solution to produce nickel particles, but nickel nanoparticles can be produced even with nickel nanoparticles, but any method for synthesizing single nanoparticles can be used. Nano colloids are optimal. Nickel colloid containing no metal other than nickel.

  The method for producing a nickel colloid according to the present invention is a method for producing a nickel colloid characterized by adding a polyol in the presence of a dispersant soluble in water or alcohol.

  The dispersant is a compound that is soluble in water or a hydrophilic alcohol and suppresses the aggregation of nickel that easily aggregates to form coarse particles. The amine is M-1000, and the acid is Examples thereof include tartaric acid derivatives, Disperbyk-2015, and the like. For nonions, polyvinylpyrrolidone and polyethylene glycol are used. These may be used alone or in combination.

  The said polyol should just be what can melt | dissolve a dispersing agent, and ethylene glycol, propylene glycol, glycerol, 1, 4- butanediol etc. are mentioned.

  When a nickel complex solution containing a reducing agent is diluted with water, the pH of the solution decreases and the reduction reaction does not proceed. However, when diluted with the same amount of glycol as the water to be diluted, the reduction reaction proceeds. It was found that a nickel ultrafine particle colloid was formed.

(Example)
EXAMPLES Hereinafter, although an Example is hung up and demonstrated in detail, this invention is not limited only to these Examples.

Example 1
(Nickel acetate / hydrazine / 1,1,3,3-tetramethylguanidine / M-1000 / PVP / dibenzoyl-L-tartaric acid / evaporation method Ni / EG)

(Adjustment of liquid A)
Nickel acetate · 4H 2 O (5.10 g, 0.0205 mol) was dispensed into a 200 ml Erlenmeyer flask, and ion exchanged water was added to make 40.0 g and dissolved. While stirring, 12.3 g (0.197 mol) of 80% hydrazine · H 2 O was dropped, and the mixture was stirred for 40 minutes to be in a suspended state to form a nickel hydrazine complex. Next, 12.6 g (0.109 mol) of 1,1,3,3-tetramethylguanidine was added and dissolved. Thereto, 60 g of M-1000 and an ethylene glycol solution of polyvinylpyrrolidone K-15 (molecular weight 10,000) prepared separately were sequentially added. Furthermore, 10.24 g of ethylene glycol solution of 0.24 g (0.00067 mol) of dibenzoyl-L-tartaric acid was added. Finally, 30 g of a 0.04 wt% nickel nanoparticle / ethylene glycol solution prepared by an evaporation method was added.

(Adjustment of B liquid)
Liquid B was prepared by mixing 210 g of dodecane and 70 g of BDG (diethylene glycol monobutyl ether).

  The tube at the outlet of the cavity of the microwave device was connected to a pressurized container, and nitrogen gas was flowed to increase the nitrogen gas pressure to 0.20 MPa.

Liquid A was fed at 5 ml / min and liquid B at 5 ml / min with a pressure-resistant plunger pump.
The target temperature was set to 130 ° C.

  The nickel particles were 150 nm or less.

  The temperature change of the reaction liquid due to microwave irradiation is plotted with temperature (° C) on the vertical axis and time (seconds) on the horizontal axis, FIG. 3 shows the data of the change in microwave intensity, and the vertical axis shows the intensity of the reflected wave (W (Watts)), and time (seconds) on the horizontal axis is shown in FIG.

  3 to 4, reference numeral 101 is a temperature curve, 101 a is a temperature curve at the time of microwave rising, 101 b is a temperature curve after microwave irradiation reaches a steady state, and 101 c is a temperature at the end of microwave irradiation due to the end of synthesis. Curve 102, the reflected wave intensity curve 102 of the microwave, 101a is the reflected wave intensity curve at the time of rising of the microwave, 101b is the reflected wave intensity curve after the microwave irradiation reaches a steady state, 101c is the micro wave upon completion of synthesis The reflected wave intensity curve at the end of wave irradiation is shown.

  The reaction temperature reached 122 ° C. in 30 seconds from the start of microwave irradiation, and was in the range of 121.5 ° C. to 137.2 ° C. after reaching a steady state. The number of times the reflected wave intensity exceeded 60 W was 28, and the number of times exceeding 100 W was 10 times.

(Comparative Example 1)
When the heating was performed at 80 ° C. using an oil bath with the same composition as in Example 1 and without microwave irradiation, nickel particles were formed, but particles of 200 nm or more were included.

(Comparative Example 2)
When the same composition as in Example 1 was used and a microwave continuous method was performed at a heating temperature of 80 ° C., nickel particles were formed, but particles of 200 nm or more were included.

(Example 2)
(Nickel acetate / hydrazine / 1,1,3,3-tetramethylguanidine / Disperbyk-2015 / dibenzoyl-L-tartaric acid / evaporation method Ni / EG)

(Adjustment of liquid A)
Nickel acetate · 4H 2 O (5.10 g, 0.0205 mol) was dispensed into a 200 ml Erlenmeyer flask, and ion exchanged water was added to make 40.0 g and dissolved. While stirring, 12.3 g (0.197 mol) of 80% hydrazine · H 2 O was dropped, and the mixture was stirred for 40 minutes to be in a suspended state to form a nickel hydrazine complex. Next, 12.6 g (0.109 mol) of 1,1,3,3-tetramethylguanidine was added and dissolved. Thereto was added 6 g of 10 wt% Disperbyk-2015 / 1,4-butanediol.
Further, 10.24 g of a 1,4-butanediol solution of 0.24 g (0.00067 mol) of dibenzoyl-L-tartaric acid was added. Finally, 30 g of a 0.04 wt% nickel nanoparticle / 1,4-butanediol solution prepared by an evaporation method was added.

(Adjustment of B liquid)
Liquid B was prepared by mixing 210 g of dodecane and 70 g of BDG (diethylene glycol monobutyl ether).

  The tube at the outlet of the cavity of the microwave device was connected to a pressurized container, and nitrogen gas was flowed to increase the nitrogen gas pressure to 0.20 MPa.

  Liquid A was fed at 5 ml / min and liquid B at 5 ml / min with a pressure-resistant plunger pump. The set temperature was set to 120 ° C.

  The nickel particles were 150 nm or less.

  A paste was prepared by increasing the metal concentration of the nickel ultrafine particle colloid to a metal concentration of about 60% by weight or more.

  A high boiling point organic solvent such as BDG (diethylene glycol monobutyl ether) having a boiling point of 230 ° C. or terpineol having a boiling point of 219 ° C. is added to the nickel ultrafine particle colloid of the dispersion medium ethanol obtained in the above description, and heated under reduced pressure. Then, ethanol was distilled off to prepare a nickel ultrafine particle paste using BDG as a dispersion medium. The organic solvent having a high boiling point is selected so that the dispersant in the nickel ultrafine particle colloid can be dissolved.

  As mentioned above, although this invention was demonstrated including the Example, this invention is not limited narrowly to these examples, Based on the technical idea of this invention, many variations are possible.

  Since the colloid and paste of the ultrafine nickel particles of the present invention are dispersed in hydrophilic alcohol and do not contain impurities that cause deterioration, electrode materials for multilayer capacitors, wiring on electronic substrates, electronic It has a great effect in a wide range of technical fields in the electronics / automotive industry, such as parts joining and nickel plating. In addition, it can be used as a catalyst for organic synthesis.

Claims (8)

Nickel formed from nickel precursor solution and the hydrazine compound - hydrazine complexes, nickel by addition of an acid dissociation constant of 13 or more amines - to an aqueous solution to form a hydroxide of hydrazine complexes, continuously irradiated with microwaves method for producing a nickel ultrafine particles colloid, characterized in that to heat. The acid dissociation constant of 13 or more amines is, the production method of the nickel ultrafine particle colloidal according to 1,1,3,3-tetramethylguanidine der Ru請 Motomeko 1. Nickel single ultrafine particles, the production method of the nickel ultrafine particles colloids according to 請 Motomeko 1 or 2 you, characterized in that added to the aqueous solution. Microwave heating, under pressure, the reaction temperature 90 ° C. or higher, the production method of the nickel ultrafine particle colloidal according to any one of the 請 Motomeko 1-3 you and performing at 170 ° C. or less. Method for producing a nickel ultrafine particle colloidal described polyols to any one of 請 Motomeko 1-4 you characterized in that added to the aqueous solution. Method for producing a nickel ultrafine particle colloidal according to any one of the 請 Motomeko 1-5 you characterized by the use of soluble dispersing agent in water and a hydrophilic alcohol. Nickel formed from nickel precursor solution and the hydrazine compound - hydrazine complexes, nickel by addition of an acid dissociation constant of 13 or more amines - to an aqueous solution to form a hydroxide of hydrazine complexes, continuously irradiated with microwaves method for producing a nickel particulate paste, which comprises to heating. Nickel single ultrafine particles, characterized in that said added to aqueous solution, the production method of the nickel particulate paste according to claim 7.

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